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Test sheds doubt on 'faster than light' claim

LIGHT SPEED BARRIER REMAINS UNBROKEN IN NEUTRINO TEST

For the moment, it seems, Einstein was still correct.

Despite fevered excitement over the past six months in the
scientific community as to whether or not the universe’s great ‘constant’ of
the speed of light might have been broken by strange particles called neutrinos,
news announced this weekend looks to have confirmed nothing still travels
faster.

Scientists studying neutrinos at the OPERA (Oscillation
Project with Emulsion tRacking Apparatus) project had been sending bursts of
the tiny particles through the earth (using a neutrino beam supplied from
CERN)to a laboratory at Gran Sasso,
730km away underneath a mountain in Italy.

To their immense surprise, preliminary results from the experiment
lastSeptember suggested that the
neutrinos – which like all things in the universe must obey the law of physics
– seemed to have arrived at the target site faster than a beam of light would
have done.

Had the neutrinos observed Einstein's laws, the subterranean
journey could not have taken longer than the 2.4milliseconds.

However they appeared to have instead arrived at Gran Sasso
60 nanoseconds - 60 billionths of a second - earlier than light.

But a test run by a different group at the same laboratory
has now clocked them travelling at precisely light speed – not faster as had
been anticipated by some.

The results in September, from the OPERA group at the Gran
Sasso underground laboratory in Italy, could have triggered the greatest
rethink in physics and cosmology in history.

Scientists have long held that the speed of light, as
predicted by Einstein in his two theories of relativity, should be the universe's
absolute speed limit.

But now, the independent ICARUS measurement, using last
year’s short pulsed beam from CERN, has reported that results indicate that the
neutrinos DO NOT exceed the speed of light on their journey between the two
laboratories.

As such, it is at odds with the initial measurement reported
by OPERA last September.

"The evidence is beginning to point towards the OPERA
result being an artefact of the measurement," said CERN Research Director
Sergio Bertolucci.

“But it's important to
be rigorous, and the Gran Sasso experiments,( BOREXINO, ICARUS, LVD and OPERA)
will be making new measurements with pulsed beams from CERN in May to give us
the final verdict.

“ In addition, cross-checks are underway at Gran Sasso to
compare the timings of cosmic ray particles between the two experiments, OPERA
and LVD.

“Whatever the result, the OPERA experiment has behaved with
perfect scientific integrity in opening their measurement to broad scrutiny,
and inviting independent measurements. This is how science works."

A web cast from CERN last September opened up the results to
the whole scientific community for scrutiny.

The ICARUS experiment measured seven neutrinos in the beam
from CERN last year. These all arrived in a time consistent with the speed of
light.

"The ICARUS experiment has provided an important cross
check of the anomalous result reports from OPERA last year," said Carlo
Rubbia, Nobel Prize winner and spokesperson of the ICARUS experiment.

"ICARUS measures
the neutrino's velocity to be no faster than the speed of light. These are
difficult and sensitive measurements to make and they underline the importance
of the scientific process.”

The Icarus experiment uses 600 tonnes - 430,000 litres - of
liquid argon to detect the arrival of neutrinos sent through 730km of rock from
the Cern laboratory in Switzerland.

It allows an accurate reconstruction of the neutrino
interactions and this technique is now recognized worldwide as the most
appropriate for future large volume neutrino detectors.

"We are completely compatible with the speed of light
that we learn at school," said Sandro Centro, co-spokesman for the Icarus
collaboration.

"Now we are 100% sure that the speed of light is the
speed of neutrinos.”

Prof Frank Close,from Exeter College, Oxford, and a world authority on particle physics,
commenting on the news, said:

“It fits in with the earlier news that OPERA had discovered
that the connections of fibre optic cables could themselves introduce an
uncertainty of tens of nanoseconds - which, in my opinion, suggests that the
original data had underestimated the uncertainties, such that the actual resultis (or was) consistent with travelling at
light speed.”